2017 年 25 巻 2 号 p. 174-179
An AMB is not widely used because of its high cost and because its dimensions are significantly larger than those of mechanical bearings. Since a 6 salient-pole type AMB has fewer poles than the usual 8 salient-pole type AMB, it is easier and less costly to miniaturize. However, because the magnetic circuit is not independent in the x and y directions, bearing forces for coil currents become complicated. To solve this problem, two control methods have been proposed. One is a minimum energy control method, which minimizes copper loss in coils. The other is a maximum bearing force control method, which generates a larger bearing force than that of the minimum energy control method. In this study, the two control methods are introduced and rotational tests are carried out for comparison. The rotor could rotate up to 53,000 rpm with the minimum energy control and maximum bearing force control methods. Moreover, rotational tests were carried out with attaching a weight to the rotor. The rotor could rotate up to 42,000 rpm and 38,000 rpm with the minimum energy control method and maximum bearing force control method, respectively. Experimental results show that the minimum energy control method provides less power consumption than the maximum bearing force control method. On the other hand, the maximum force control method provides smaller maximum coil current than that of the minimum energy control method.
